(This version of the October 4 story corrects first paragraph to show that ricin is not a bacteria; corrects day of week in 4th paragraph; spelling of Plexiglas in paragraph 13)
By Alex Dobuzinskis
(Reuters) - A letter sent to the Pentagon this week containing castor seeds, from which the highly toxic ricin poison is derived, shows the daily challenges facing the U.S. Postal Service and companies trying to stay a step ahead of potentially deadly deliveries.
After letters containing deadly anthrax were mailed to two senators and media outlets in 2001, the U.S. Postal Service began irradiating mail addressed to the White House, the U.S. Congress and other government offices.
Irradiation destroys bacteria, such as anthrax, and viruses that could be present in mail. But ricin remains dangerous even after irradiation, the Centers for Disease Control and Prevention says.
On Wednesday, authorities in Utah arrested a Navy veteran in connection with letters sent to the Pentagon containing castor seeds, which by themselves do not pose a threat. The U.S. Secret Service has said another letter was intercepted before reaching the White House, though it did not disclose if that letter also contained castor seeds.
The motivation behind the letter sent to the Pentagon is as yet unclear. But few of these kinds of threats are related to terrorism, experts say.
“People often think of a mail bomber as a person motivated by radical political beliefs. This stereotype is incorrect,” the U.S. Postal Office said on its website.
Letter or package bombs usually target specific individuals, - jilted spouses, former business partners or employees, and law enforcement and judicial figures targeted by individuals who have been prosecuted, according to the Postal Service.
U.S. government buildings have sporadically received packages with suspected ricin, including in 2013 when ricin-laced letters were addressed to the White House, a U.S. senator and a Mississippi justice official.
In response to the threat of explosives and hazardous substances, the U.S. Postal Inspection Service has a number of teams that use of portable X-ray machines and other measures to investigate suspicious parcels, the agency said in a statement.
“The U.S. Postal Service has developed a comprehensive approach to protecting the mail system by utilizing a targeted strategy of specialized technology, screening protocols and employee training,” it said.
The statement declined to give details on other strategies used by the Postal Inspection Service, citing concerns against compromising its methods.
For corporate headquarters in the United States, other security measures are often in place to guard against dangers in the mail, said Hugh O’Rourke, vice president of consulting services for the MSA Security firm.
Those may include a safe box a person can use to open a suspicious letter by using rubber gloves while looking through Plexiglas, O’Rourke said.
A number of companies also use X-ray machines to allow operators, who are sometimes security experts looking at a monitor from an off-site location, to see what is inside a parcel, O’Rourke said.
Some companies find it essential to process their mail at a safe location before bringing it to their headquarters, O’Rourke said.
In other cases, the processing center may be a basement room with negative air pressure flow to keep toxins from spreading to other areas, he said.
Despite such advances, technology to screen for dangerous mail is not in use everywhere.
“A lot of places basically rely far too much on somebody finding something odd as they begin opening something,” said Anthony Cordesman, a security analyst at the Center for Strategic International Studies. “The primary screening device is the person who opens it.”
Reporting by Alex Dobuzinskis in Los Angeles; editing by Bill Tarrant and Dan Grebler